--- a/js/src/jit/x64/MacroAssembler-x64-inl.h
+++ b/js/src/jit/x64/MacroAssembler-x64-inl.h
@@ -15,30 +15,35 @@ namespace js {
 namespace jit {
 
 //{{{ check_macroassembler_style
 // ===============================================================
 
 void
 MacroAssembler::move64(Imm64 imm, Register64 dest)
 {
-    // Wipe out the top bit to avoid any potential sign extension problems
-    uint64_t blind = 0x7FFFFFFF7FFFFFFFULL & js::GenerateRandomSeed() ;
-    uint32_t blind_top = 0x7FFFFFFF & (blind >> 32);
-    uint32_t blind_bot = 0x7FFFFFFF & (blind);
+    // Do not blind common constants that are (believed to be) safe
+    if(int64_t(imm.value) >= int64_t(-32768) && int64_t(imm.value) <= int64_t(32767)) {
+        movq(ImmWord(imm.value), dest.reg);
+    } else {
+        // Wipe out the top bit to avoid any potential sign extension problems
+        uint64_t blind = 0x7FFFFFFF7FFFFFFFULL & js::GenerateRandomSeed();
+        uint32_t blind_top = 0x7FFFFFFF & (blind >> 32);
+        uint32_t blind_bot = 0x7FFFFFFF & (blind);
 
-    uint64_t blinded = imm.value ^ blind;
-    // pre-rotate to save us one emitted assembly instruction
-    blinded = (blinded >> 32) | (blinded << 32);
+        uint64_t blinded = imm.value ^ blind;
+        // pre-rotate to save us one emitted assembly instruction
+        blinded = (blinded >> 32) | (blinded << 32);
 
-    movq(ImmWord(blinded), dest.reg);
+        movq(ImmWord(blinded), dest.reg);
 
-    xorq(Imm32(blind_top), dest.reg);
-    rorq(Imm32(32), dest.reg);
-    xorq(Imm32(blind_bot), dest.reg);
+        xorq(Imm32(blind_top), dest.reg);
+        rorq(Imm32(32), dest.reg);
+        xorq(Imm32(blind_bot), dest.reg);
+    }
 }
 
 void
 MacroAssembler::move64(Register64 src, Register64 dest)
 {
     movq(src.reg, dest.reg);
 }
 

--- a/js/src/jit/x86-shared/MacroAssembler-x86-shared.h
+++ b/js/src/jit/x86-shared/MacroAssembler-x86-shared.h
@@ -122,24 +122,30 @@ class MacroAssemblerX86Shared : public A
         else
             vucomiss(rhs, lhs);
     }
 
     void branchNegativeZero(FloatRegister reg, Register scratch, Label* label, bool  maybeNonZero = true);
     void branchNegativeZeroFloat32(FloatRegister reg, Register scratch, Label* label);
 
     void move32(Imm32 imm, Register dest) {
-        uint32_t blind = js::GenerateRandomSeed();
-        uint32_t blinded = imm.value ^ blind;
-
         // Use the ImmWord version of mov to register, which has special
         // optimizations. Using uint32_t here ensures that the value
         // is zero-extended.
-        mov(ImmWord(blinded), dest);
-        xorl(Imm32(blind), dest);
+
+        // Do not blind common constants that are (believed to be) safe
+        if(int32_t(imm.value) >= int32_t(-32768) && int32_t(imm.value) <= int32_t(32767)) {
+            mov(ImmWord(uint32_t(imm.value)), dest);
+        } else {
+            uint32_t blind = js::GenerateRandomSeed();
+            uint32_t blinded = imm.value ^ blind;
+
+            mov(ImmWord(blinded), dest);
+            xorl(Imm32(blind), dest);
+        }
     }
     void move32(Imm32 imm, const Operand& dest) {
         movl(imm, dest);
     }
     void move32(Register src, Register dest) {
         movl(src, dest);
     }
     void move32(Register src, const Operand& dest) {